Sorry… I have had seasons of major back and joint problems too with my ankylosing spondelytis… Not easy…
As far as the harsh prairie climate:
Jujube is new to me but it is my #1 hopeful tree once my trees are established… I am putting effort into them!!
My 2nd tree I am not sure but I may would go with either hardy early pears like the harrow types or hardy early american persimmons like yates or perhaps early hardy hybrids like NB-02. Of course I’m planting them all lol… Persimmons probably bloom a bit later than pears and are very hardy trees once established.
Stone fruits are bad on late spring frosts…, some cultivars are better later blooming, but I dont know, they are much lower on my list, my peaches get froze often even my reliance…